The present disclosure relates to transmitters suitable for a low-power semiconductor memory device, and more particularly, to an open loop source follower voltage transmitter and a driving voltage controlling method thereof.
The recent development of high-speed and low operating power semiconductor memory devices have caused the manner in which signals are transferred from a transmitter within a semiconductor memory device to be changed from high voltage swing signaling into low voltage swing signaling.
A transmitter that is generally placed within an output circuit of the semiconductor memory device may be formed by a regulator that generates a regulated driving power and an output driver that receives the driving power and transmits data to an output terminal.
A typical regulator may be formed of a common source circuit and a PMOS transistor is mainly used as a current driving element. The current driving strength of a PMOS transistor may be lower than that of an NMOS transistor, and can be significantly changed according to power supply VDD variations. For this reason, a power supply rejection ratio (PSRR) of the PMOS transistor, which is a log ratio of output noise to input noise, may be relatively inferior as compared with the PSRR of an NMOS transistor.
Accordingly, regulators have been implemented by a source follower circuit with a current driving element having an NMOS transistor. In this case, an amplifier is typically needed to provide the gate of the NMOS transistor with a gate voltage higher than a power supply voltage, and, as a result, power consumption may be increased when an operation mode is executed in a closed loop fashion.
Accordingly, a need exists for a transmitter having a low-power, simplified regulator as a driving power generator.